Expansion board apparatus and removing method

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application of filed co-pending parent application Ser. No. 10/154,115 filed with the United States Patent and Trademark Office on May 23, 2002, as attorney docket number JP920010230US1 the teachings of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an expansion board, expansion board for communication, insulating film for expansion board, computer system, expansion board removing method, and electronic circuit board, and more particular to apparatus and method for such to be employed with computer systems.

2. Description of Related Art

In recent years, so-called PCs (personal computers) have come to be provided with more and more diversified functions. For example, many of those PCs are provided with functions for communicating with external just by connecting such an expansion device as a modem board, a LAN board, etc. to them. Those expansion devices are classified into two types; built-in type and external type. The built-in type device is installed inside the subject PC while the external type device is connected to the subject PC from outside. Users often select and install necessary expansion devices by themselves according to their requirement. For a built-in type device, the user is required to expose the PC by removing the case and connect the board type expansion device to the connector of the mother board inside the PC.

However, some expansion devices cannot be installed by users. Concretely, those devices are small expansion devices for lap-top PCs. Because portability is an very important item for lap-top PCs, those expansion devices are limited in size. Consequently, parts are packed at a high density thereon, so that the lap-top PCs become complicated in internal structure. In addition, expansion devices must be installed/removed very accurately and carefully. This is why usually the PC makers install those small expansion devices in lap-top PCs; no consideration is given to the installation of those devices by users from the beginning.

In spite of this, year after year there have increased users who want to expand the capability of their lap-top PCs more freely and accordingly, those users come to desire to install those small expansion devices by themselves. It would therefore be a significant advantage for those users if they could install/remove those expansion devices that are comparatively expensive small expansion devices and mother boards etc. by themselves.

SUMMARY OF THE INVENTION

Under such circumstances, it is an object of the present invention to solve the above conventional technical problems and provide an expansion board, which enables users to connect/disconnect expansion devices to/from mother boards of those lap-top PCs.

In order to attain the above object, in one aspect, the expansion board of the present invention, connected to the mother board of the subject computer system, is intended to expand the functions of the computer system. The expansion board of the present invention comprises a first face facing the mother board; a second face that is the back of the first surface; and a projection formed by a flexible sheet extended from the second face so as to be separated therefrom. The user can connect/disconnect the small expansion board to/from a predetermined position inside the subject PC smoothly by taking this protruded sheet with fingers. The shape of the flexible sheet is not limited specially; it is just required for the user to be able to take it with fingers. For example, the flexible sheet may be a narrow strap-like one.

Furthermore, in another aspect, the expansion board of the present invention to be employed for computer systems includes two surfaces; face and back. On the back is provided a connector used to connect the mother board of the subject computer system and on the face is provided a grip used to take the expansion board with fingers.

The present invention, in a further aspect, may also be considered as a communication expansion board. In this case, the communication expansion board comprises a board provided with a primary area used to connect an external network and a secondary area used to connect a portion inside the subject computer, an insulating film used to cover at least the primary area, and a projection provided with a fixed end fixed to the face of the insulating film and a free end formed so as to be separated from the insulating film.

The projection may be formed by extending the insulating film. In such a case, the insulating film is wound on the communication expansion board in the width direction and the projection is extended in the longitudinal direction of the board so as to cross the width direction. The projection may also be formed by a dedicated sheet separately from the insulating film. In such a case, the fixed end of the projection may be formed by connecting one end of the dedicated projection sheet to the insulating film. The projection may also be formed by winding the dedicated projection sheet on the communication expansion board, then connecting both ends of the sheet to each other.

The present invention in still a further aspect may also be considered as an insulating film for the communication expansion board. The insulating film used for the communication expansion board includes a cover portion used to cover the face of the communication expansion board and a projection extended from the fixed end on the face of the cover portion to external and enabled to be taken with fingers.

Furthermore in another aspect, the present invention may be considered as a computer system. The computer system comprises accepting means for accepting an expansion board removably; processing means for processing data of the expansion board connected to the accepting means; board holding means located on the face of the expansion board and enabled to be held by the user so as to connect/disconnect the board to/from the accepting means. This board holding means is preferably configured so that the user can remove the board from the accepting means easily.

The computer system of the present invention also includes a mother board and an expansion board connected to the mother board. The mother board includes processing means and an expansion board connector used to connect the board and send/receive data to/from the processing means. The expansion board includes a mother board connector used to connect the mother board and an extended sheet extended from the face of the expansion board.

In the computer system, the communication channel used for the communication with an external network is extended from the processing device and connected to the expansion board connector. The communication channel may include one of a modem channel, a LAN channel, and a wireless LAN channel.

Furthermore in another aspect, the present invention may also be considered as a method for disconnecting the expansion board from the mother board connector. According to the method, the user takes grip of the expansion board with fingers and pulls it so as to disconnect and remove the board from the mother board connector connected to the back of the board.

Further, for another aspect, the present invention may also be considered as an electronic circuit board. The electronic circuit board comprises first and second main faces that face each other; a connector located on the first main face and enabled to connect an external device; and a flexible sheet located on the face of the electronic circuit board. Part of the flexible sheet is connected to the electronic circuit board and another part thereof is extended so as to be separated from the second main face. When an electronic circuit is mounted on this electronic circuit board, at least part of the electronic circuit can be covered by the flexible sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, features, and advantages of the present invention will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings in which:

FIG. 1 is a hardware block diagram of a computer system in an embodiment of the present invention;

FIGS. 2A and 2B are an expanded view of a CDC; FIG. 2A is a top view from the face and FIG. 2B is a top view from the back;

FIG. 3 is a perspective view of the CDC that is not covered by an insulating film;

FIG. 4 is a top view of the insulating film;

FIG. 5 is an expanded cross sectional view of the CDC connected to its mother board;

FIG. 6 is a perspective view of the CDC of which projection is taken by fingers;

FIG. 7 is a top view of the projection formed position;

FIG. 8 is a top view of the CDC in another embodiment;

FIG. 9 is a perspective view of the CDC in still another embodiment; and,

FIG. 10 is a perspective view of the CDC in still another embodiment.

DETAILED DESCRIPTION

The use of figure reference labels in the claims is intended to identify one or more possible embodiments of the claimed subject matter in order to facilitate the interpretation of the claims. Such labeling is not to be construed as necessarily limiting the scope of those claims to the embodiments shown in the corresponding figures. The preferred embodiments of the present invention and its advantages are best understood by referring to the drawings, like numerals being used for like and corresponding parts of the various drawings

Hereunder, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a hardware block diagram of a computer system (computer apparatus) <b>10</b> in a first embodiment of the present invention. The computer apparatus provided with this computer system <b>10</b> is configured as a lap-top PC (Personal Computer) conforming, for example, to the OADG (Open Architecture Developer's Group) specifications and employs a predetermined OS (Operating System).

The computer system <b>10</b> shown in FIG. 1 is composed of a CPU (Central Processing Unit) <b>11</b> mounted on the mother board; a CPU bridge <b>15</b>; an I/O bridge <b>21</b>; a main memory <b>16</b>; a PCI (Peripheral Component Interconnect) bus <b>20</b> used to connect various components; an ISA (Industry Standard Architecture) bus <b>40</b>; and an FSB (Front Side Bus) <b>12</b>. The mother board is provided with connectors and slots used to connect such expansion boards as a PC card <b>24</b>; a mini-PCI device <b>60</b>; a daughter card <b>70</b> provided with functions for communications with external (hereinafter, to be described as the Communication Daughter Card (CDC)), etc., thereby the computer system <b>10</b> comes to have various additional functions. Hereunder, the configuration of the computer system <b>10</b> will be described concretely.

In the computer system <b>10</b> shown in FIG. 1, the CPU <b>11</b> mounted on the mother board functions as the brain of the whole computer system <b>10</b> and executes various programs under the control of the OS. The CPU <b>11</b> is connected to each component of the computer system <b>10</b> via three steps of busses as the system bus FSB <b>12</b>, the PCI bus <b>20</b> used for fast I/O devices, and the ISA bus <b>40</b> used for slow I/O devices. The CPU <b>11</b> stores program codes and data in a cache memory so as to process them fast. In recent years, an SRAM of about 128 KB is often provided in the CPU <b>11</b> as a primary cache. In addition, for a secondary cache <b>14</b>, about 512K to 2 MB is spared in the CPU <b>11</b> and used via a dedicated bus BSB (Back Side Bus) <b>13</b>. The BSB <b>13</b> may be omitted and the secondary cache <b>14</b> may be connected to the FSB <b>12</b>.

The FSB <b>12</b> and the PCI bus <b>20</b> are connected to each other via a CPU bridge (host-PCI bridge) <b>15</b> referred to as a memory/PCI chip. This CPU bridge <b>15</b> is configured so as to have memory controller functions for controlling the accesses to the main memory <b>16</b>, a data buffer for absorbing the data transfer speed difference to generate between the FSB <b>12</b> and the PCI bus <b>20</b>, as well as others.

The main memory <b>16</b> is used as an area for reading programs to be executed by the CPU <b>11</b> or as an area for writing data processed by those programs. For example, the main memory <b>16</b> is configured by a plurality of DRAM chips and it can be expanded as needed. The programs to be executed by the CPU <b>11</b> include various hardware drivers used to operate the OS, as well as various peripheral devices, application programs dedicated to specific business works, and such firmware programs as the BIOS (Basic Input/Output System) stored in a flash ROM <b>44</b> to be described later, etc.

The video subsystem <b>17</b> is used to execute video-related functions. The video subsystem <b>17</b> includes a video controller. This video controller processes drawing instructions received from the CPU <b>11</b> and writes processed drawing information in a video memory and reads the drawing information from the video memory so as to output the information onto the liquid crystal display (LCD) <b>18</b> as drawing data.

The PCI bus <b>20</b> enables data to be transferred comparatively fast. The PCI bus <b>20</b> is standardized so that the data bus width is set to 32/64 bits, the maximum operation frequency is set to 33/66 MHz, and the maximum data transfer speed is set to 132 MB/sec/528 MB/sec respectively. The I/O bridge (core bridge) <b>21</b>, the card bus controller <b>22</b>, the audio subsystem <b>25</b>, the docking station interface (Dock I/F) <b>26</b>, and the mini-PCI connector (expansion board connector) <b>27</b> are connected to this PCI bus <b>20</b> respectively.

The card bus controller <b>22</b> is used exclusively to connect the bus signal of the PCI bus <b>20</b> directly to the interface connector (card bus) of the card bus slot <b>23</b>. The PC card <b>24</b> can be connected to this card bus slot <b>23</b>. This PC card <b>24</b> is a kind of a device for expanding the capability of the computer system <b>10</b>. The PC card <b>24</b> enables a device to be connected to the dedicated card bus slot <b>23</b> from outside without exposing the computer system <b>10</b>.

The docking station interface (Dock I/F) <b>26</b> is a hardware component used to connect a docking station (not shown), which is a capability expansion device of the computer system <b>10</b>. When a lap-top PC is set at the docking station, various hardware components connected to the internal bus of the docking station can be connected to the PCI bus <b>20</b> via the docking station interface <b>26</b>.

The mini-PCI device <b>60</b> is connected to the mini-PCI connector <b>27</b>. The mini-PCI device <b>60</b> is an expandable capability expansion card (board) conforming to the mini-PCI specifications. The “mini-PCI” means a mobile PCI standard; it is described as a supplement to the PCI Rev. 2.2 specification. Functionally, the mini-PCI is equivalent to the full specification PCI. In addition, the mini-PCI connector <b>27</b> connects an AC '97 (Audio CODEC '97) link extended from the I/O bridge. The AC '97 link is one of the specifications of sound devices and modem devices for the PCI bus. Usually, the AC '97 link has two channels. One of the two channels is assigned to a sound device and the other is assigned to a modem device.

The I/O bridge <b>21</b> is provided with a bridging function for the bridging between the PCI bus <b>20</b> and the ISA bus <b>40</b>. The I/O bridge <b>21</b> is also provided with the DMA controller function, the programmable interruption controller (PIC) function, the programmable interval timer (PIT) function, the IDE (Integrated Device Electronics) interface function, the USB (Universal Serial Bus) function, and the SMB (System Management Bus) interface function. The I/O bridge <b>21</b> also incorporates a real time clock (RTC) in itself.

The DMA controller function enables data transfer between such peripheral devices as an FDD, etc. and the main memory <b>16</b> not via the CPU <b>11</b>. The PIC function enables a predetermined program (interruption handler) to be executed in response to an interruption request (IRQ) from each of the peripheral devices. The PIT function generates timer signals at predetermined cycles. Each interface realized by the IDE interface function is connected to an IDE hard disk drive (HDD) <b>31</b>, as well as a CD-ROM drive <b>32</b> via an ATAPI (AT Attachment Packet Interface). Instead of this CD-ROM drive <b>32</b>, another type IDE device such as a DVD (Digital Versatile Disk) drive may be connected to the interface. Such external storage devices as the HDD <b>31</b>, the CD-ROM drive <b>32</b>, etc. are housed in a place in the subject lap-top PC. The place is usually referred to as a “media bay” or “device bay”. Those external storage devices attached to the PC as standard might possibly be replaceable with such other devices as an FDD, a battery pack or attached exclusively.

The I/O bridge <b>21</b> is also provided with a USB port. The USB port is connected to a USB connector <b>30</b> located, for example, on a wall of the lap-top PC body. In addition, an EEPROM <b>33</b> is connected to this I/O bridge <b>21</b> via the SM bus. This EEPROM <b>33</b> is a non-volatile memory used to hold information such as a user-registered password, a supervisor password, the product serial number, etc. The data in the EEPROM <b>33</b> can thus be rewritten electrically. The I/O bridge <b>21</b> is also connected to a power supply circuit <b>50</b>. The power supply circuit <b>50</b> is provided with an AC adapter <b>51</b>; a battery changing circuit <b>54</b> used to charge the battery (second battery) (the main battery <b>52</b> or second battery <b>53</b>) and change the power supply path from the AC adapter <b>51</b>/each battery; a DC/DC converter <b>55</b> used to generate such DC constant voltages as 5V, 3.3V, etc. used for the computer system <b>10</b>.

The I/O bridge <b>21</b> is also connected to a CDC connector <b>28</b> used to connect a CDC. This CDC connector <b>28</b> is connected to a CDC (expansion board, communication expansion board) <b>70</b>. The CDC <b>70</b> is a capability expansion daughter board dedicated for communications with external. In this embodiment, the CDC <b>70</b> is used as a LAN board conforming to the Ethernet standard (hereinafter, to be described as a LAN CDC provided with the LAN function). Signals are exchanged between the CDC connector <b>28</b> and the I/O bridge <b>21</b> in accordance with the Ethernet interface standard. Concretely, the LAN interface converts analog signals received from the CDC <b>70</b> to digital signals through the PHY (Physical Layer) and the digital signals are converted and processed by a MAC (Media Access Controller) in accordance with the Ethernet protocol. The CDC <b>70</b> is smaller than the mini-PCI device <b>60</b> in size. For example, the CDC <b>70</b> has an area of about 1/2.5 of the mini-PCI device <b>60</b>.

In addition to the LAN interface, AC '97 link and USB (Universal Serial Bus) interfaces are provided between the I/O bridge <b>21</b> and the CDC connector <b>28</b>. Consequently, in addition to the Ethernet standard LAN board, the CDC connector <b>28</b> can connect a CDC <b>70</b> provided with the modem board function conforming to the AC '97 link specifications (hereinafter, to be described as a modem CDC) or such a CDC <b>70</b> as a USB (Universal Serial Bus) standard wireless LAN board, etc. (hereinafter, to be described as a LAN CDC).

The ISA bus <b>40</b> is slower than the PCI bus <b>20</b> in data transfer rate (for example, bus width: 16 bits, maximum data transfer rate: 4 MB/sec). This ISA bus <b>40</b> is connected to the embedded controller <b>41</b> connected to the gate array logic <b>42</b>; the CMOS <b>43</b>; the flash ROM <b>44</b>; and the super I/O controller <b>45</b> respectively. This ISA bus <b>40</b> can also be connected to such peripheral devices as a keyboard/mouse controller, which are comparatively slow in operation. The super I/O controller <b>45</b> is connected to the I/O port <b>46</b> and used to drive an FDD and control the input/output of parallel data (PIO) via a parallel port and the input/output of serial data (SIO) via a serial port. The embedded controller <b>41</b> controls a keyboard (not shown) and some of the power management functions.

Next, for a particular aspect, the configuration of the CDC <b>70</b> is described.

FIG. 2 is an expanded view of the CDC <b>70</b> shown in FIG. <b>1</b>. FIG. <b>2</b>(<i>a</i>) is a top view from the face (second face) and FIG. <b>2</b>(<i>b</i>) is a top view from the back (first face). FIG. 3 is a perspective view of the CDC <b>70</b> that is not covered by the insulating film. FIG. 4 is another top view of the CDC <b>70</b> for denoting the shape of the insulating film. FIG. 5 is an expanded cross sectional view of the CDC <b>70</b> for denoting how the CDC <b>70</b> is connected to the mother board <b>100</b>.

The CDC <b>70</b> is used for a LAN and composed of a board <b>80</b> and an insulating film <b>90</b> that covers the face of the board <b>80</b> as shown in FIG. <b>2</b>(<i>a</i>). The CDC <b>70</b> has two surfaces; the face <b>80</b><i>s </i>and the back (on which an IC is mounted) <b>80</b><i>t </i>that are faced each other. The approximate size of the CDC <b>70</b> is 45 mm (x direction: length) 28 mm (y direction: width) for example. As shown in FIGS. 3 and 5, the board <b>80</b> is composed of a connector part <b>81</b> used to connect the CDC connector <b>28</b> on the mother board <b>100</b>; holes <b>85</b><i>a </i>and <b>85</b><i>b </i>used to fix the board <b>80</b> onto the mother board <b>100</b> with screws; and an I/O connector part <b>82</b> used to connect a modular connector RJ-45 used to connect an external network. Those items of the CDC <b>70</b> are all located on the back <b>80</b><i>t</i>. In FIG. 3, the detailed description of the circuits on the back <b>80</b><i>t </i>of the board <b>80</b> is omitted. The connector part <b>81</b> of this CDC <b>70</b> is connected to the CDC connector <b>28</b> on the mother board <b>100</b> while the circuit-mounted side <b>100</b><i>t </i>of the mother board <b>100</b> faces the back <b>80</b><i>t </i>of the CDC <b>70</b> as shown in FIG. <b>5</b>.

In the CDC <b>70</b>, the primary circuit <b>88</b> in which the I/O connector part <b>82</b> of the board <b>80</b> exists might receive a high voltage caused by lightning from an external network connected thereto via the modular connector RJ-45 while the modular connector RJ-45 is connected to the I/O connector part <b>82</b>. In order to avoid such a trouble, therefore, the primary area <b>88</b> of the board <b>80</b> may be covered by the insulating film <b>90</b> as shown in FIG. <b>2</b>. The insulating film <b>90</b> is made of, for example, such a flexible sheet as polypropylene sheet or the like. The insulating sheet is preferably within about 0.05 to about 0.1 mm in thickness so as not to increase the total thickness of the CDC <b>70</b> body.

In order to cover the board <b>80</b> by the insulating film <b>90</b> as shown in FIGS. 2A and 2B, for example, the insulating film <b>90</b> cut into a shape as shown in FIG. 4 is wound on the board <b>80</b> so that both x and y directions are aligned at the primary area <b>88</b> of the board <b>80</b>. The length of the insulating film <b>90</b> is enough to go round the board <b>80</b> once in the y direction and cover the primary circuit <b>88</b> in the x direction. Then, the insulating film <b>90</b> is wound on the board <b>80</b> so that the rear edge part <b>90</b><i>b </i>of the insulating film <b>90</b> is almost aligned to the rear edge part <b>80</b><i>b </i>of the board <b>80</b> and the position of the hole <b>91</b> formed in the insulating film <b>90</b> is aligned to the position of the hole <b>85</b><i>b </i>of the board <b>80</b>. After this, the side edge parts <b>90</b><i>d </i>and <b>90</b><i>c </i>of the insulating film <b>90</b> wound on the board <b>80</b> are put on top of one another and stuck with an adhesive. As a result, the primary area <b>88</b> is covered and the secondary area is exposed in the CDC <b>70</b> as shown in FIG. <b>2</b>B. In the secondary area is provided a connector part <b>81</b> used to connect the CDC connector <b>28</b> located on the mother board <b>100</b>.

At this time, the insulating film <b>90</b> has a projection <b>95</b> protruded outside the front edge part <b>90</b><i>a </i>in the x direction. In the CDC <b>70</b>, this projection <b>95</b> is located on the face <b>80</b><i>s </i>of the board <b>80</b> as shown in FIG. <b>2</b>A. The user can take this projection <b>95</b> with fingers as shown in FIG. 6 so as to connect/disconnect the CDC <b>70</b> to the CDC connector <b>27</b> of the mother board <b>100</b> and carry the CDC <b>70</b> with him/her.

Hereinafter, the shape of the projection <b>95</b> is further described. The dimensions of the projection <b>95</b> are, for example, 12 mm (<b>95</b><i>w </i>(width of the fixed end))×9 mm (<b>95</b><i>d </i>(length from the fixed end to the free end). When the insulating film <b>90</b> is wound on the board <b>80</b>, the distance d between the tip of the projection <b>95</b> and the front end of the board <b>80</b> is 1 mm. To make it easier to take the projection with fingers, the width <b>95</b><i>w </i>of the projection <b>95</b> is preferably 7 mm or over, further preferably be 10 mm or over. On the other hand, the length <b>95</b><i>d </i>of the projection <b>95</b> is preferably 7 mm or over so as to make it easier to take the portion with fingers. While the upper limits of both width <b>95</b><i>w </i>and length <b>95</b><i>d </i>are not limited specially, the width <b>95</b><i>w </i>and the length <b>95</b><i>d </i>is preferably 30 mm or less and 35 mm or less respectively so that the projection <b>95</b> is not become an obstacle when the CDC <b>70</b> is installed in a computer system <b>10</b>.

The projection <b>95</b> shaped as described above is positioned so as to make it easier to apply a force to the connector part <b>81</b> on the back <b>80</b><i>t</i>, so that the CDC <b>70</b> connected to the CDC connector <b>28</b> of the mother board <b>100</b> as shown in FIG. 5 is disconnected easily from the mother board <b>100</b> upward by taking the projection <b>95</b> of the CDC <b>70</b> with fingers as shown in FIG. <b>6</b>. Concretely, the point of the force should preferably comes to the center of the connector part <b>81</b> when the projection <b>95</b> is pulled up.

In this embodiment, the vertical center line <b>96</b><i>n </i>that divides the projection <b>95</b> into two parts in the y direction is aligned to the vertical center line <b>81</b><i>n </i>that divides the connector part <b>81</b> into two parts in the y direction. The distance between the horizontal center line <b>81</b><i>m </i>that divides the connector part <b>81</b> into two parts in the x direction and the base end <b>96</b> of the projection <b>95</b> is set to about 5 mm. Because the base end <b>96</b> of the projection <b>95</b> is positioned around the connector part <b>81</b>, it is easy to disconnect the CDC <b>70</b> from the CDC connector <b>27</b> of the mother board <b>100</b>.

Furthermore, to make it easier to disconnect the CDC <b>70</b> from the CDC connector <b>27</b> of the mother board <b>100</b>, the base end center <b>96</b><i>c </i>that divides the base end <b>96</b> of the projection <b>95</b> into two parts in the y direction is preferably positioned in an installation area <b>87</b> shown in FIG. <b>7</b>. The installation area <b>87</b> has a predetermined distance in the y and x directions from the center <b>81</b><i>c </i>of the connector, which is a node of the vertical center line <b>81</b><i>n </i>and the horizontal center line <b>81</b><i>m </i>of the connector part <b>81</b>. The predetermined distance on the face <b>80</b><i>s </i>is preferably within 10 mm from a position corresponding to the connector center <b>81</b><i>c </i>Furthermore, each of the distances <b>87</b><i>a </i>and <b>87</b><i>b </i>in the y direction is preferably 5 mm or under. The distance <b>87</b><i>d </i>between the connector center <b>81</b><i>c </i>and the front end <b>80</b><i>f </i>of the board <b>80</b> in the x direction is preferably 4 mm or under (the distance between the connector center <b>81</b><i>c </i>and the front end <b>80</b><i>f </i>of the board <b>80</b>) and the distance <b>87</b><i>c </i>between the connector center <b>81</b><i>c </i>and the rear end <b>80</b><i>e </i>of the board <b>80</b> in the x direction is preferably 10 mm or under.

In the case of the insulating film <b>90</b>, corners <b>94</b><i>a </i>and <b>94</b><i>b </i>that are boundaries between the front edge part <b>90</b><i>a </i>and the projection <b>95</b> thereof are curved. Because the corners <b>94</b><i>a </i>and <b>94</b><i>b </i>are curved such way, when an attempt is made to disconnect the CDC <b>70</b> from the mother board <b>100</b> by taking the projection <b>95</b> with fingers as shown in FIG. 6 while the CDC <b>70</b> is connected to the CDC connector <b>28</b>, a force applied to the corners <b>94</b><i>a </i>and <b>94</b><i>b </i>of the insulating film <b>90</b> is not concentrated at a point so much. This is why the endurance of both corners <b>94</b><i>a </i>and <b>94</b><i>b </i>of the insulating film <b>90</b> is improved. Consequently, when the projection <b>95</b> is pulled with fingers, the insulating film <b>90</b> is prevented from being lengthened and cut off at the corner <b>94</b><i>a</i>/<b>94</b><i>b</i>. The curvature R of the curved corners <b>94</b><i>a </i>and <b>94</b><i>b </i>is preferably 5 to 8 mm or so.

The shape of the corners <b>94</b><i>a </i>and <b>94</b><i>b </i>may be changed. For example, just like the corners <b>94</b><i>c </i>and <b>94</b><i>d </i>of the CDC <b>70</b>A shown in FIG. 8, each of the corners <b>94</b><i>a </i>and <b>94</b><i>b </i>may be formed obliquely towards the projection <b>95</b><i>a </i>from the front edge <b>90</b><i>a </i>of the insulating film <b>90</b>A. The shape may also be right-angled. Such the insulating film <b>90</b>A may be made of a sheet strong enough so as not to be cut off when the CDC <b>70</b>A connected to the CDC connector <b>28</b> is pulled off by taking the projection <b>95</b><i>a </i>with fingers.

The connector part <b>81</b> of the CDC <b>70</b> is connected to the CDC connector part <b>28</b> of the mother board <b>100</b> such way. On the other hand, the connector part of a flexible cable (not shown) is connected to the I/O connector part <b>82</b> of the CDC <b>70</b>. The other end of the flexible cable is connected to the modular connector RJ-45 so as to be connected to an external network.

When the computer system <b>10</b> is powered by the user in this state, an ID signal is output from the mother board connector part <b>81</b> of the CDC <b>70</b> via an output pin of the GPIO (General Purpose Input/Output) pins to an input pin of the I/O bridge <b>21</b>. The ID signal communicates the main memory <b>16</b> about that the CDC <b>70</b> is a LAN board. The GPIO pins are used to input/output general signals and the GPIO-pin state can be changed freely with use of a software program (CDC driver, etc.). The GPIO is used for communications with other chips. In this embodiment, a specific type CDC is assigned to each of the GPIO pins. Consequently, an ID signal issued when the CDC <b>70</b> is connected turns off a predetermined pin assigned to the LAN board ID signal beforehand at the input side of the GPIO of the I/O bridge <b>21</b>. Then, the mother board (host) <b>100</b> outputs information that the CDC <b>70</b> connected to the CDC connector <b>28</b> is identified as a LAN board to the main memory <b>16</b> via the I/O bridge <b>21</b>.

As a result, the computer system <b>10</b> recognizes the CDC <b>70</b> as a device that functions as a LAN board, thereby executing processings appropriately to the CDC <b>70</b> used as a LAN board.

As described above, the CDC <b>70</b> connected to the mother board <b>100</b> as shown in FIG. 5 enables the computer system <b>10</b> to make communications via the LAN (CDC <b>70</b>). In this case, because the CDC <b>70</b> has the projection <b>95</b> formed with the insulating film <b>90</b>, the user can adjust the position of the CDC <b>70</b> to the CDC connector <b>27</b> easily by taking the projection <b>95</b> with fingers, thereby the user can connect the CDC <b>70</b> to the mother board <b>100</b> easily. When disconnecting the CDC <b>70</b> from the CDC connector <b>27</b> of the mother board <b>100</b>, the user can also do the work easily by pulling the projection <b>95</b>. Consequently, the use of the CDC <b>70</b> will make it easier to expand the functions of the computer system <b>10</b> and replace the functions of the computer system <b>10</b> with others easily.

Furthermore, because the projection <b>95</b> is formed by extending the insulating film <b>90</b> in the above embodiment, the manufacturing cost can be reduced more than that of any of the conventional insulating films that are not provided with any projection. In addition, such the projection <b>95</b> can be formed easily in the above embodiment.

FIG. 9 is a perspective view of another CDC provided with another shaped projection in another embodiment of the present invention.

In the CDC <b>70</b>B shown in FIG. 9, a projection film <b>98</b> is wound outside the insulating film <b>90</b>B that covers the board <b>80</b>. The insulating film <b>90</b>B is not provided with the projection <b>95</b>, which is formed at the insulating film <b>90</b> in the CDC <b>70</b> shown in FIG. <b>2</b>(<i>a</i>). Around the front edge <b>90</b><i>a </i>of this insulating film <b>90</b>B is wound the projection film <b>98</b>. Both films <b>90</b>B and <b>98</b> are stuck at mutual contact portion by an adhesive so as to form a projection <b>98</b><i>t</i>. In this case, both films <b>98</b> and <b>90</b>B may be stuck all over or partially at those mutual contact portions. The projection <b>98</b><i>t </i>is made of the same insulating sheet material as that of the insulating film <b>90</b>B. They may also be made of different materials.

The projection <b>98</b><i>t</i>, because it is protruded outside from the back <b>80</b><i>t </i>of the board <b>80</b>, is easy for the user to take with fingers. The height <b>98</b><i>d </i>of the projection formed on the face of the insulating film <b>90</b>B is about 8 mm and the width <b>98</b><i>w </i>of the insulating film <b>90</b>B is about 14 mm. Just like the CDC <b>70</b>, the base end <b>98</b><i>b </i>of the projection <b>98</b><i>t </i>is preferably positioned around a portion corresponding to the center of the connector part <b>81</b> (not shown in FIG. 9) formed on the back <b>80</b><i>t </i>even for this CDC <b>70</b>B.

As described above, the projection <b>98</b><i>t </i>may also be formed with a material different from that of the insulating film <b>90</b>B for insulating the board <b>80</b>. Such way, the insulating film enables the projection <b>98</b><i>t </i>to be shaped and positioned freely when the projection <b>98</b><i>t </i>is formed with a non-continuous material. Consequently, the projection <b>98</b><i>t </i>can be positioned so as to make it easier for the user to take and easier for a disconnecting force to work on the connector part <b>81</b>. This is why the user can disconnect the CDC <b>70</b>B from the CDC connector <b>27</b> of the mother board <b>100</b>.

While the CDC <b>70</b> has been described as a LAN CDC in the above embodiment, the insulating film <b>90</b> may also apply to a modem CDC employed as the CDC <b>70</b>. While the insulating film <b>90</b> is wound on the board <b>80</b> just once in the LAN CDC <b>70</b>, it may be wound twice. Especially, when the CDC <b>70</b> is used as a modem CDC, the insulating film <b>90</b> should be wound more than twice so as to assure the insulation.

FIG. 10 is a perspective view of still another CDC in still another embodiment of the present invention. The CDC is provided with a projection whose shape differs from those in the above embodiments.

The CDC <b>70</b>C shown in FIG. 10 is a wireless LAN CDC. In this case, unlike the LAN CDC and the modem CDC that must be insulated, there is no need to insulate the CDC. The surface of the wireless LAN CDC is thus covered by no insulating film. And, a projection <b>95</b><i>c </i>is formed with a fixed tape <b>99</b> on the board <b>80</b> as shown in FIG. <b>10</b>. At this time, the fixed tape <b>99</b> is preferably positioned on the board <b>80</b> where no such components as circuits are placed. And, because the fixed tape <b>99</b> requires only a very small area, the fixed tape <b>99</b> is preferably such a strong double-sided adhesive tape or the like. On the other hand, the sheet that forms the projection <b>95</b><i>c </i>is preferably a low stiffness one difficult to be cut off at the base end <b>96</b>. Preferably, the sheet that forms the projection <b>95</b><i>c </i>should be a flexible sheet made of the same material as that of, for example, the insulating film <b>90</b> used for the CDC <b>70</b>.

Because the base end <b>96</b> is fixed to the surface of the board even at the CDC <b>70</b>C that requires no insulating film in this embodiment as described above, the projection <b>95</b><i>c </i>can be formed easily. The user can thus take the projection <b>95</b><i>c </i>of the CDC <b>70</b>C so as to connect/disconnect the CDC <b>70</b>C to/from the CDC connector <b>27</b> of the mother board <b>100</b> easily.

It is also possible to form the projection at the above-described wireless LAN CDC by covering both face and back of the CDC just like the LAN CDC.

While the computer system <b>10</b> in this embodiment is provided with only one CDC connector <b>27</b> that connects the CDC <b>70</b>/<b>70</b>A/<b>70</b>B/<b>70</b>C, the present invention can apply to a computer system provided with a plurality of CDC connectors used to connect a plurality of CDCs.

While a description has been made only for the CDC in this embodiment, the present invention can apply to such expansion boards as the mini-PCI device, the MDC, etc. The functions of the expansion board of the present invention, to be added to the computer system <b>10</b>, are not limited only to functions of communications with external; the functions may be those of video cards, memories, etc.

In addition to those described above, obviously many more modifications and variations of the present invention are possible without departing from the spirit of the present invention.